1. Field of the Invention
This invention generally relates to a rotating servomotor apparatus for use in a hydraulic machine and more particularly to a driving apparatus to rotate wicket gates for controlling water flow.
2. Description of the Prior Art
In general, a rotating servomotor apparatus of this type, as shown in FIG. 1 is attached to a spindle 3 provided with wicket gates 2 and functions to control the openings of the wicket gates 2 or to maintain a constant degree of opening of the wicket gates or guide vanes. As shown in FIG. 2, stationary partition members 5 extend radially inwardly from a servo-cylinder 4 of a rotating servomotor 1 and partition a plurality of compartments 7a, 7b . . . 7h in cooperation with movable partition members 6 disposed on a spindle 3.
The stationary position members 5 disposed on the servo-cylinder 4 consist of four equally spaced partitions arranged at 90.degree. intervals. Four movable partition members 6 corresponding to the number of stationary partition members 5 also are provided, so that within the rotating servo-cylinder 4 are formed eight compartments 7a, 7b . . . 7h. Openings 8a, 8b . . . 8h corresponding to the above-described respective compartments are provided through respective portions of the circumferential wall of the rotating servo-cylinder 4.
Also shown schematically in FIG. 2 are passages 12a and 12b having respective ends connected to fluid-supply openings 11a and 11b disposed on a distributing valve 10 which has a valve piston 9 inserted therein. The other end of passage 12a is connected to the openings 8a, 8c, 8e and 8g of the rotating servo-cylinder 4, and the other end of passage 12b is connected to the openings 8b, 8d, 8f, and 8h of the rotating servo-cylinder 4. The openings 8a, 8b . . . 8h are alternately connected in the circumferential direction to the fluid-supply openings 11a and 11b of a distributing valve 10. Further, the distributing valve 10 is provided with an inlet passage (solid line) to receive fluid from a fluid-supply port (not shown), and outlet passages (dotted line) to drain fluid from the servomotor 1.
When the valve piston 9 is actuated upwardly, for example, fluid such as oil under pressure is supplied from the distributing valve 10 into the compartments 7a, 7c, 7e and 7g which are partitioned by the movable partition members 6 and the stationary partition members 5. The movable partition members 6 are then rotated to cause the wicket gates to be opened, and when the wicket gates are to be closed, the reverse operations are made.
When the valve piston 9 is positioned in a neutral position, the wicket gates 2 are caused to maintain a constant degree of opening. The relationship between the opening degree of wicket gates and the hydraulic moment developed at the wicket gate spindle, as shown in FIG. 3, illustrates that when such hydraulic moment reaches near zero, the wicket gates are in equilibrium.
Therefore, the rotating servomotors of the above-described type are susceptible to accurrence of flow-induced vibrations at the wicket gates, and this causes the occurrence of noises or even damage of various members in hydraulic machines.